Distribution patterns of PFASs in intertidal sediments and the effects on reductive dehalogenating bacteria: A nationwide study in China

Per- and polyfluoroalkyl substances (PFASs) are of great concern because of their environmental persistence. The intertidal zone sequesters various halogenated organic pollutants (HOPs) in sediments. Microbial reductive dehalogenation is crucial for HOPs detoxification. However, the nationwide distribution characteristics of PFASs in intertidal sediments and their impact on reductive dehalogenators (RDGs) remain poorly understood. We investigated PFAS distribution profiles in 128 intertidal sediments across China and analyzed their impact on potential RDGs. Sedimentary PFAS concentrations ranged 0.049-2.58 ng/g, with legacy PFASs being dominant. Amplicon sequencing and Spearman rank correlation analysis revealed positive correlation between total organic halogens and relative abundance and/or α-diversity of Anaerolineae and Desulfobacterota (p < 0.05), whereas no correlation was observed for Dehalococcoidia. Despite low ecological risks, Cl-PFESAs showed significant negative correlations with their relative abundance and α-diversity. Cl-PFESAs negatively correlated with abundance of the module associated with elemental cycles (p < 0.05), rather than those linked to organohalide utilization in the co-occurrence network. Microbial cultivation and metagenomic analysis reinforced the crucial role of Desulfobacterota and Anaerolineae in intertidal microbial dehalogenation and the negligible effect of 6:2 Cl-PFESA (0.1 mg/L) on reductive dehalogenating activity. This study provides critical insights into bioremediation strategies for HOPs in intertidal zones co-contaminated with PFASs.